Fluid control system for tractor trailer brake system

ABSTRACT

A fluid control system for use with vehicles, in particular, trailers, includes a branch conduit (19, 25, 42, 80, 96) which is to be connected to a pressure supply line (20) and a control line (22) to enable priming of the control line (20) so that signals generated upon application of the vehicle brake pedal are more quickly transmitted to the trailer brakes. This overcomes problems associated with delay in application of the trailer brakes. An electrically operated solenoid valve (11) controls fluid flow through the branch conduit so that upon application of the vehicle brake pedal the solenoid valve is operated to open the branch conduit to allow pressurized fluid to flow from the supply line (20) to the control line (22) for a predetermined time period to prime the control line (22). Pressurized fluid from the branch supply conduit is directed longitudinally down the control line (22) by a longitudinally arranged outlet (35, 57) so that substantially all of the fluid is directed to backfill the control line. The system may be embodied in a block arrangement in which bores are drilled in a block housing and in which the branch conduit (19, 25) is formed by passages drilled in the block or may be formed from discrete hose sections and couplings.

This is a division of application Ser. No. 08/512,413 filed Aug. 8,1995, which issues May 20, 1997 as U.S. Pat. No. 5,630,655 which is adivision of application Ser. No. 08/196,158 filed Feb. 22, 1994, nowU.S. Pat. No. 5,464,278.

This invention relates to improvements in control systems utilisingworking fluids, and in particular to pneumatic or hydraulic brakingsystems such as may be found on vehicles and in particular on semitrailers, trucks and the like.

Australian patent application number 41104/89 discloses brake systemsfor prime movers and trailers and discuss problems associated withcompressed air brake system design and, in particular, premature brakelining wear in a prime mover which results when predominantly gentlebraking takes place. The earlier applications propose a system in whichcompressed air is fed into a brake control line which controlsapplication of the trailer brakes in order to "prime" the trailer brakessystem so that there is minimal delay in brake application after thebrake pedal is depressed by a driver. The brake control line carries asignal from the foot pedal of the prime mover to a relay valve toactivate the relay valve so pressurised fluid can flow from a reservoirwhich is supplied by a supply line to eventually activate a brake. Theinvention disclosed in the earlier applications has been found tosignificantly overcome problems associated with delay in application ofthe trailer brakes during gentle braking and therefore braking lead ismore evenly distributed between the brakes of the prime mover and thetrailer thereby decreasing brake lining wear on the prime mover and alsoproviding smoother and enhanced braking characteristics.

Since brake lining wear is associated with the prime mover rather thanthe trailer, and since prime movers and trailers are often owned bydifferent organisations, it is of more concern to the owner of the primemover to enhance braking characteristics of the trailer. The systemsdescribed in the above Australian patent application propose theinjection of pressurised air in the control line at or near the relayvalve associated with the trailer brakes. It would be advantageous toallow for injection into the brake control line at the location of theprime mover so that the pneumatic or hydraulic circuitry can beassociated with the prime mover rather than the trailer and without theneed for additional connection of pneumatic or hydraulic lines andelectric cables above that which is normally required when connecting atrailer to a prime mover. Incorporation of the required hydraulic orpneumatic lines in the prime mover which would provide for the abovementioned priming of the trailer brake system would enable the primemover to be used with conventional trailers and would also ensure thatthe owner of the prime mover has the advantage of equalising brakingload during gentle braking and therefore reducing brake wear on theprime mover.

A first aspect of the invention relates to a fluid control system for abraking system which may be installed in conventional braking systems toprovide for priming of a trailer braking system.

The first aspect of the invention therefore provides a fluid controlsystem for a brake system including a supply line, a control line andbrake application detection means, comprising:

a housing;

a first conduit supported by the housing;

a second conduit supported by the housing;

attachment means coupled to the first conduit for enabling the firstconduit to be coupled in the supply line;

second attachment means coupled to the second conduit to enable thesecond conduit to be coupled in the control line;

a passage connecting the first conduit to the second conduit; and

fluid control means actuatable by the brake application detection meansfor selectively allowing fluid to flow through the passage from thefirst conduit to the second conduit; wherein

when the fluid control means is actuated by the brake applicationdetection means the fluid control means allows fluid to flow from thesupply line and first conduit through the passage to the second conduitand control line to enable backfilling of the control line with fluid.

The fluid control system of the first aspect of the invention can bereadily fitted to prime movers, trailers or other vehicles or devicesespecially where the control line and supply line associated with theprime mover and trailer are in close proximity. Because the passages andconduits are supported by a housing the fluid control system is veryrobust.

In one embodiment of the invention the first conduit and second conduitmay comprise hoses or conduits which are fixed to and supported in ahousing. However, in the preferred embodiment of the invention thehousing comprises a housing block and the first conduit comprises afirst bore through the housing block, the second conduit comprises asecond bore through the housing block and the passage is a passagewaybored in the housing for connecting the first bore to the second bore.

In the preferred embodiment of the invention the arrangement of thebores and passage within the block housing lends itself to massproduction in NC lathes and the like which can minimise productioncosts.

Preferably the block has a cavity and the fluid control means isconnected to the cavity to close the cavity to define a chamber, thepassage comprising a first passage portion leading from the first boreto the chamber and a second passage portion leading from the chamber tothe second bore, the fluid control means having a valve element whichshuts off the second passage portion and when actuated by the brakeapplication detection means the valve element moves away from the secondpassage portion to allow fluid to flow through the first passage portioninto the chamber through the second passage portion and into the secondbore.

Preferably the fluid control means comprises a solenoid valve.

Preferably the cavity has a screw thread and the solenoid valve has amating screw thread so that the solenoid valve can be connected to thehousing block by interengagement of the screw threads.

Preferably the brake application detection means comprises electricwiring from a brake light system and electronic controller for actuatingthe solenoid valve for a predetermined time period.

In the prior art systems described above, it has been found that theinjection of compressed air into a control line upstream from a relaydoes not provide as good results as when the compressed air is injectedin the vicinity of the relay. We expect this occurs because thecompressed air is introduced into the control line by virtue of aT-piece and therefore only half the air travels down the control linewith the remainder of the air travelling in the opposite direction to bevented to atmosphere.

An object of the second aspect of the invention is to overcome thisproblem.

The invention in a second aspect provides a fluid control system for abraking system including a relay valve for receiving a supply ofpressurised fluid from a supply line and a control line for supplying acontrol signal to the relay valve to actuate the relay valve to enablepressurised fluid to flow from the supply line to vehicle brakes toactuate the vehicle brakes, comprising:

a conduit for coupling between a source of pressurised fluid and saidcontrol line;

a control valve for selectively allowing pressurised fluid to flowthrough the conduit, said control valve being actuatable in response toa braking event to enable pressurised fluid to flow through the conduitand into the control line; and

an outlet of the conduit being positioned relative to the control linesuch that pressurised fluid exiting the conduit and entering the controlline is directed in the longitudinal direction of the control line.

Since the conduit has its outlet in the longitudinal direction of thecontrol line, pressurised fluid which enters the control line to primethe trailer brake system is directed down the control line therebyenabling the control line to be filled to the desired priming volume orpressure even when the conduit is coupled to the control line remotefrom the relay valve. The positioning of the conduit outlet in thedirection of the longitudinal axis of the control line ensures thatsubstantially all of the air in the conduit is injected down the controlline and is used to prime the control line when the conduit joins thecontrol line remote from the relay valve. Thus, problems which areassociated with joining the conduit to the control line by aperpendicular part of a T-piece where only half the air flows into thecontrol line to prime the control line are overcome. Thus, the fluidcircuitry can be associated with the prime mover remote from the relayvalve on the trailer while still providing adequate priming of thetrailer brake system and thereby overcoming delay in application of thetrailer brakes during gentle braking applications.

A third aspect of the invention concerns the provision of fluidcircuitry and a method of installation which can be associated with theprime mover so that for all intents and purposes when a trailer isconnected to the prime mover the connection of the fluid lines isperformed in a conventional manner and which will nevertheless stillprovide priming of the control line to thereby prime the trailer brakingsystem.

This aspect of the invention also provides a method of providing abraking system with a fluid control system for priming the brakingsystem, the braking system including a supply line, a control line andan electrical signal line, the method comprising:

providing a fluid control system which includes a supply conduit, acontrol conduit and a passage joining the supply conduit and the controlconduit, and an electrically operated control valve for selectivelyallowing fluid to flow through the passage;

coupling the supply conduit in the supply line so that fluid in thesupply line can flow through the supply line and also into the supplyconduit;

coupling the control conduit in the control line so that fluid in thecontrol line can flow through the control conduit and also into thecontrol line; and

electrically connecting the electrically operated control valve to theelectrical signal line;

wherein upon generation of an electrical signal in the electrical signalline the control valve is actuated to allow fluid to pass from thesupply line and supply conduit through the passage and into the controlconduit and control line to backfill the control line and prime thebraking system.

The supply conduit and control conduit may be coupled in the supply lineand control line respectively by locating the fluid control systembetween a prime mover and a trailer so that the fluid control system isconnected to the conventional connectors associated with the prime moverand the conventional connectors associated with the trailer, or may belocated at an existing joint in the control line and supply line.However, in another embodiment of the invention the supply conduit andcontrol conduit are coupled in the supply line and control line bymaking a cut in the supply line and control line and connecting thesupply conduit and control conduit in the supply line and control linerespectively.

This aspect of the invention also provides a fluid circuit forconnection in a control fluid line and a supply fluid line comprising:

a fluid branch conduit having a first end and a second end, the firstend having a control fluid inlet and a control fluid outlet, and thesecond end having a supply fluid inlet and a supply fluid outlet, thecontrol fluid inlet and control fluid outlet being for connection in thecontrol line, and the supply fluid inlet and supply fluid outlet beingfor connection in the supply line; and

a control valve arranged in said fluid branch conduit to selectivelyallow fluid flow through the branch conduit.

In one embodiment of the invention the fluid branch conduit comprises aflexible hose and the control fluid inlet and control fluid outletcomprise a first connector and a second connector of a different type tothe first connector respectively, and the supply fluid inlet and thesupply fluid outlet comprise a first connector and a second connector ofa different type to the first connector respectively.

In another embodiment the fluid circuit includes a block housing whichhas a fluid control bore therethrough and a fluid supply boretherethrough, said fluid branch conduit comprising a passageinterconnecting the control bore with the supply bore, one end of thecontrol bore having an attachment member forming the fluid inlet and theother end of the control bore having attachment member forming thecontrol fluid outlet, one end of the supply bore having an attachmentmember forming the supply fluid inlet and the other end of the supplybore having an attachment member forming the supply fluid outlet, saidcontrol valve being mounted to the block housing for selectively openingand closing said passage.

This aspect of the invention thereby provides a conduit system which canbe connected to a prime mover and which will present a conventionalcontrol line outlet and fluid supply outlet for connection to a controlline and supply line of a trailer whilst at the same providing a branchconduit which can prime the control line in response to a gentleapplication of the prime mover brakes so that there is no delay inapplication of the trailer brakes during gentle braking and so thatbraking load is evenly distributed between the trailer and the primemover.

Preferably the control valve is a solenoid valve and is coupled to brakelight electrical circuitry for actuating the control valve when a brakepedal is depressed.

Preferably the fluid control system also includes an electrical circuitcomprising an electrical connector for connection to the electricaloutput from the prime mover a parallel circuit between the connector andthe control valve for actuation of the control valve, and an electricaloutput connection for connection to the electric circuit of the trailer.

In one preferred embodiment of the invention where the branch supplyconduit is long or prone to damage the control valve is connected inclose proximity to the supply line and the branch conduit includes acheck valve which is connected in close proximity to the control line.Thus, should any damage occur to the branch supply conduit the checkvalve will prevent egress of air from the control line and the controlvalve prevents uncontrolled egress of air from the supply line.

Preferred embodiments of the invention will be described, by way ofexample, with reference to the accompanying drawings in which:

FIG. 1 is a schematic view of a prime mover and trailer with which thepreferred embodiment of the invention is used;

FIG. 2 is a cross-sectional view of a control system according to thepreferred embodiment of the invention;

FIG. 3 is a front view of the system of FIG. 1;

FIG. 4 is a side view of the system of FIG. 1;

FIG. 5 is a schematic view of a fluid control system and an electricalsystem according to a second embodiment of the invention;

FIG. 6 is a detailed view of the fluid control circuitry of FIG. 5;

FIG. 7 is a schematic view relating to installation of the device ofpreferred embodiments;

FIG. 7A shows installation of a device according to one embodiment;

FIG. 7B shows installation of a device according to another embodiment;

FIG. 8 shows an arrangement according to a further embodiment; and

FIG. 9 shows an arrangement according to a still further embodiment.

With reference to FIG. 1 a prime mover 10 and trailer 12 are shown. Thetrailer 12 has a relay valve 14 which supplies pressurised fluid tobrakes (not shown) associated with rear wheels 18 to cause the brakes tobe applied. The trailer 12 also has a pressurised fluid supply line 20which supplies a reservoir 15, and a control line 22. The trailer 12also has a control line connector 24 associated with line 22 forconnection to a control line output 26 associated with the prime mover10. The trailer 12 also has a connector 28 associated with pressuresupply line 20 for connection with a connector 30 of a pressure supplyline associated with the prime mover 10. The trailer 12 still furtherhas an electrical connection 32 for connection with an electricalconnector 34 associated with the prime mover 10 for providing electricsignals on a circuit 17 to activate the trailer brake lights 19 andother lights associated with the trailer.

Conventionally, when the trailer 12 is coupled with the prime mover 10the connectors 24 and 26, 28 and 30 and 32 and 34 are merely connectedtogether as described above to supply the required fluid controlsignals, supply fluid and electrical signals to the trailer 12. However,according to the preferred embodiment of this invention a fluid controlsystem and electrical connector system schematically shown as 40 in FIG.1 is connected to the connectors 26, 30 and 34 of the prime mover.

With reference to FIGS. 2 to 4 a control system 40 according to thefirst embodiment of the invention is shown for connection in the supplyline 20, control line 22 and electrical circuit 17.

In this embodiment the system 40 comprises a housing block 1 formed fromsteel or other suitable material. The housing block 1 has bores 3 and 5drilled through it. The housing block is provided with a cavity 17a anda drilled passage 19 extends from the cavity 17a to the bore 3. A secondpassage 25 is drilled in the block 1 and extends from the cavity 17a tothe bore 5. The cavity 17a is provided with screw threads 13 for screwthreaded attachment of a solenoid valve 11. An electronic control box 51is associated with the solenoid valve 11 for actuating the solenoidvalve 11.

The solenoid valve 11 is provided with a screw threaded connecting bolt15a which is screw threaded to the screw threads 13 to attach thesolenoid valve 11 to the block 1 and close the cavity 17a.

The bores 3 and 5 are provided with connectors 7 and 9 at each end sothat the connectors 7 at the ends of the bore 3 can be connected toconnectors 28 and 30 associated with the prime mover and trailer shownin FIG. 1 and the connectors 9 associated with the bore 5 can beconnected with the connectors 24 and 26 associated with the prime moverand trailer shown in FIG. 1. The block 1 therefore acts to connect thecontrol line from the prime mover to the control line of the trailer andalso the supply line from the prime mover to the supply line of thetrailer. In an alternative embodiment the control system 40 shown inFIGS. 2 to 4 my be connected permanently with the trailer by makingappropriate cuts in the supply line 20 and control line 22 associatedwith the trailer and coupling the cut ends of the supply line 20 to theconnectors 7 associated with the bore 3 and the cut ends of the controlline 22 to the connectors 9 associated with the bore 5. In this mannerthe block 1 is permanently coupled in the control and supply lines 20and 22 of the trailer shown in FIG. 1 and the connectors 24, 26, 28 and30 need only be connected together in the conventional manner when thetrailer 12 is coupled to the prime mover 10.

Electrical connectors 32 and 34 may be coupled to control box 51associated with the solenoid valve 11 or the electrical circuit 17 maybe broken into and connected to the control box 51.

The solenoid valve 11 has an armature 64 and a core 63 which carries arubber valve element 27. The core 63 is able to move in the valve 11when the valve 11 is energised. The block 1 is provided with a firstpassage section 19 drilled from a base of the cavity 17a to the bore 3and a second passage section 25 drilled from the base of the cavity 17ato the bore 5. A hollow insert 21 is located in the passage 25 andextends up into the closed cavity 17a. When the solenoid valve 11 is notenergised the valve element 27 seats on the end of the insert 21 toprevent fluid flow from the passage 19 to the passage 25 to preventfluid flow from the bore 3 to the bore 5 and therefore from the supplyline 20 to the control line 22. However, when the brake pedal in theprime mover 10 is depressed, an electric signal in the circuit 17 issupplied to the control box 51 which in turn powers the solenoid valve11 to cause the core member 63 to move away from the insert 21 in thedirection of arrow A in fibre 2 so that pressurised air in the supplyline 20 and therefore the bore 3 can pass through the passage 19, theconduit 17a, the insert 21 and into the bore 5 and thus into the controlline 22 to backfill the control line and therefore prime the trailerbrake system.

The insert 21 is provided with an outlet opening 35 at its outlet end asis shown in FIG. 2. The outlet 35 is directed in the longitudinaldirection of the bore 5 so that the air which passes from the bore 3 tothe bore 5 is directed down the control line 22 in the longitudinaldirection of the control line 22 to backfill the control line 22. Theadvantage and purpose of directing the fluid flow in the longitudinaldirection of the control line 22 will be further described withreference to the embodiment shown in FIGS. 5 and 6.

The control box 51 causes the solenoid valve 11 to activate only for apredetermined time interval so that sufficient pressurised fluid canflow from the bore 3 to the bore 5 to backfill the control line 22 andtherefore prime the control line 22. After the predetermined timeinterval has elapsed the solenoid valve 11 is deactivated so that thecore 63 moves in a direction opposite to the arrow A so that valveelement 27 seals off the insert 21 to prevent fluid from flowing fromthe bore 3 to the bore 5.

The block 1 may also be provided with through holes 29 and 31 which arearranged perpendicular to the bores 3 and 5 and which pass through theblock 1 without interfering with the bores 3 and 5. The holes 29 and 31are intended to receive bolts or other fasteners for enabling the block1 and therefore the control system 40 to be suitably fastened to aparticular part of the vehicle or trailer with which it is used.

A cover 33 may be located around the control box 51 and secured to theblock 1 by one or more of the bolts or fasteners (schematically shown as15b in FIG. 2) which pass through the holes 29 and 31. The cover 33 isprovided with an opening 33a for location on a nut or plug 68 (which inthis embodiment seals the valve 11) and which may be retained in placeby that nut or a further fastener to thereby not only provide a coverfor the control box 51 but also to secure the solenoid valve 11, controlbox 51 and the block 1 together.

FIG. 5 shows a second embodiment of the system 40 which includes a fluidbranch conduit 42 which may comprise a flexible hose and which has apressurised fluid inlet 44, a pressurised fluid outlet 46, a controlfluid inlet 48 and a control fluid outlet 50. The branch conduit 42 alsoincludes a solenoid valve 52.

The system 40 also includes an electrical connector 54 which has aninput plug 56, an output plug 58 and a parallel electric circuit 60connected to the control box 51 of the solenoid valve 52. The controlfluid inlet 48 is coupled to the connector 26 on the prime mover, thepressurised fluid inlet 44 is connected to the connector 30 on the primemover and the input plug 56 is connected to the electrical connector 34on the prime mover.

The control fluid outlet 50 and pressurised fluid outlet 46 arepresented to the trailer and are configured to be standard connectoroutlets which are normally associated with the prime mover and which canbe directly coupled to the connectors 24 and 28 respectively. Similarly,connector plug 58 is adapted to be coupled with connector 32 on thetrailer to provide electrical energy to the trailer 12. Thus, for allintents and purposes once the system 40 is connected to the prime movera person connecting the trailer 12 to the prime mover will merely bepresented with the conventional fluid connectors and electricalconnectors which would normally be associated with the prime mover forsupplying the required fluid signals and electrical signals to thetrailer 12.

With reference to FIG. 6 which shows the branch conduit 42 in moredetail, it can be seen that inlet 48 is arranged at an angle withrespect to the branch conduit 42. In the embodiment shown the inlet 48is at right angles to the conduit 42 but it could be arranged at aninclined angle between 0 and 90 degrees and preferably at about 45°. Theconnector 24 of the fluid control line 22 which connects over outletconnector 50 will therefore be coaxial with the branch conduit 42 sothat the outlet 57 of the branch conduit 42 is directed in thelongitudinal axial direction of the control line 22 when the connector50 is connected with the connector 24.

The outlet 57 of the branch conduit 42, in the embodiment shown in FIG.6, is defined by the end of a tube 59. The tube 59 has an inlet end 60which is arranged adjacent a valve element 62 of the solenoid valve 52.The solenoid valve 52 is connected in the branch line 42 by an armature64 which has a passage 66 therethrough. The armature 64 is located inplace by a nut 68 which also secures a bolt 67 which is joined to aflexible hose portion 41 of fluid conduit 42 by a further nut 70.

The other end of the hose portion 41 is connected to pressurised fluidinlet 44 which forms a T-branch with pressurised fluid outlet 46.

As previously mentioned the control line outlet 50 and the pressurisedfluid outlet 46 are conventional outlet connectors which a prime moveris normally equipped with for connection to corresponding connectors ona trailer. Thus, pressurised fluid is supplied from the inlet 44 intothe conduit 42 and out of the outlet 46 to the pressurised fluid line 20where it is controlled by relay valve 14 for application to the brakesassociated with wheels 18 of the trailer 12. The relay valve 14 iscontrolled by control signals supplied on control line 22 to selectivelycause the relay valve 14 to open to allow the pressurised fluid inreservoir 15 to pass to the brakes via portion 20a of the supply line 20associated with the wheels 18. The supply fluid is also supplied in thebranch conduit 42 through the flexible hose portion 41 to the solenoidvalve 52.

When a driver applies the prime mover brakes the electrical signal whichis generated to activate the brake lights 19 (FIG. 1) associated withthe trailer 12 is supplied to connector 56 (FIG. 2) and thereforeelectrical signals are applied on parallel circuit 60 to the electricalcontrol box 51 of the solenoid valve 52. This activates the solenoidvalve 52 so that core member 63 to which valve element 62 is connectedis moved away from the end 60 of the tube 59. Pressurised air thereforeis able to flow through the hose 41, the nut 70, bolt 67, passage 66about the core 63 and into the tube 59 where it is injected into thecontrol line 22 in a direction substantially parallel to thelongitudinal axis of the control line 22 through connector 50 andconnector 24. Since the pressurised fluid is injected into the fluidcontrol line 22 in the direction of its longitudinal axis the momentumof the pressurised fluid results in substantially all of the pressurisedfluid passing into the control line 22 and substantially none of thepressurised fluid flowing back out through the inlet 48. Thus, injectionof the pressurised air into the fluid control line 22 in the directionof its longitudinal axis results in rapid priming of the fluid controlline 22 so than control signals generated upon application of vehiclebrakes are rapidly supplied to the relay valve 14 to cause operation ofthe trailer brakes.

Although in the preferred embodiment of the invention the tube 59 isprovided which has an outlet end 57 slightly downstream of the positionwhere the inlet 48 joins the conduit 42, it would be possible to providea shorter tube 59 or no tube at all since the injection of thepressurised fluid in the longitudinal direction of the line 22 willensure that substantially all of the fluid flows into the line 22 andnot out through the inlet 48.

The preferred embodiment of the invention thereby provides a system forenabling a prime mover to be plumbed so that when a conventional traileris connected to it the braking system of the trailer can be primed toensure that there is no lag in application of the trailer brakes duringgentle braking of the prime mover. Thus, the brakes of the prime moverare not unduly worn and general braking efficiency of the prime movertrailer combination is improved.

Although in this embodiment of the invention it is preferred to arrangethe tube 59 so that it is coaxial with the portion of the control line22 downstream from the tube 59, it would be possible to arrange the tube59 or outlet from the branch supply line 42 so that it is at an angleand effectively forms a Y-join with the control line. This would stillresult in the outlet being directed down the control line andsubstantially all, if not totally all, of the pressurised fluid in thesupply conduit 42 being directed down the control line.

FIGS. 7, 7A and 7B show how the preferred fluid supply system shown inFIGS. 2 and 5 can be installed into the control line and supply line ofa prime mover/trailer combination. As is shown in FIG. 7, cuts 66 and 68are made in the supply and control lines respectively and at 70 and 72in the electric circuit 17.

FIG. 7A shows how a fluid control system generally of the type shown inFIG. 5 can be installed. As previously described the supply line 20supplies compressed air from a source of compressed air (not shown) inthe direction of arrow A to a reservoir 15 (see FIG. 1) at the rear ofthe trailer. A control line 22 transmits pneumatic signals from the footvalve (not shown) in the prime mover also in the direction of arrow A tothe relay valve 14 (see FIG. 1) in the trailer. Electrical lines 17carry electrical signals which are initiated when the brake pedal isdepressed in the prime mover to the brake lights 19 (see FIG. 1) also inthe direction on arrow A.

At a convenient position on the trailer where all 4 lines 20, 22 and 72are in reasonably close proximity cuts 66, 68, 70 and 72 are made. Aconventional T-piece 74 is inserted into the cut 66 of the supply line20. A conventional T-piece 76 is inserted into the cut 68 of the controlline 22. An electrical connector block 78 is inserted into the cuts 70and 72 of the wires 17. A branch supply conduit 80 (FIG. 7A) connectsthe T-piece 74 to the inlet 82 of the control valve 84. The outlet 86 ofthe control valve 84 is connected to the T-piece 76. Wires 88 from thecontrol valve 84 are joined to the appropriate portions of the connectorblock 78. Having been installed in this way, the fluid control system 40can be deactivated, say by an electrical component failure, without anyeffect on the integrity of operation of the brake system. Also thecontrol circuit 40 doe snot effect the brakes generally except duringthe first 2 seconds of brake application. This arrangement is also easyto install and remove if necessary. Of course, the described T-piecesand connector block could also be inserted between existing joiningcomponents.

FIG. 7B shows how the device shown in FIG. 2 is installed. The connectorblock 17 is joined into the circuit 17 and the cut ends of the lines 20and 22 are coupled to the connectors 7 and 9 associated with the bores 3and 5.

With reference to FIGS. 8 and 9, like numerals represent likecomponents. FIG. 8 schematically represents the General arrangementdescribed in earlier embodiments. Control valve 92 is connected in closeproximity to the control line 22. The branch supply conduit 96 connectsthe control valve 92 to the supply line 20. Electrical wires (not shown)carry the electrical signal to activate the control valve 92. Insituations where the branch conduit is long or prone to damage, theimproved arrangement schematically in FIG. 9 has the control valve 92connected in close proximity to the supply line 20. A check valve 98 isconnected in close proximity to the control line 22. The branch supplyconduit 96 connects the check valve 98 to the control valve 92.Electrical wires (not shown) connect to the control valve 92 in theusual way. The check valve 98 is of conventional design and isorientated to allow a flow of compressed air from the control valve 96to the control line 22, but blocks flow in the opposite direction.Preferably, the check valve would be built near the outlet of the branchsupply conduit where the compressed air is directed down the controlline.

With this arrangement, should any damage occur to the branch supplyconduit 96 the check valve 98 prevents egress of air from the controlline 22, and the control valve 92 prevents uncontrolled egress of airfrom the supply line 20.

Although in the preferred embodiment the system has been disclosed forconnection between a prime mover and a trailer and it would be possibleto use the system in road trains where the branch supply conduit 42 isinstalled between trailers of the road train.

Since modifications within the spirit and scope of the invention mayreadily be effected by persons skilled within the art, it is to beunderstood that this invention is not limited to the particularembodiment described by way of example hereinabove.

The claims defining the invention are as follows:
 1. A vehicle brakesystem for a vehicle which includes a tractor and a trailer which can beconnected to and disconnected from the tractor, said brake systemincluding:a relay valve for supplying fluid to brakes of the vehicle toactivate the vehicle brakes; a fluid supply coupled to the relay valveso that, upon actuation of the relay valve, supply fluid is suppliedfrom the fluid supply via the relay valve to the vehicle brakes toactuate the vehicle brakes; a control line having a first control lineportion which is coupled to the tractor and a second control lineportion which is coupled to the trailer, and which is decoupled from thetractor when the trailer is disconnected from the tractor, the firstcontrol line portion having a first connector and the second controlline portion having a second connector for detachable connection to saidfirst connector so that the first and second control line portions canbe coupled together when the trailer is connected to the tractor, thecontrol line being coupled to the relay valve so that upon depression ofa brake pedal in the tractor, a control signal is supplied down thecontrol line to the relay valve to actuate the relay valve; and fluidsupply means for supplying fluid from the fluid supply to the controlline to prime the control line when the brake pedal is depressed, thefluid supply means being connected to the tractor.
 2. The fluid controlsystem according to claim 1, wherein:the fluid supply means includes anozzle having an outlet directed in the longitudinal direction of thecontrol line for supply of the fluid from the fluid supply in thelongitudinal direction of the control line.
 3. The fluid control systemaccording to claim 2, wherein the fluid supply further includes asolenoid valve for selectively enabling the fluid to flow from the fluidsupply to the control line.
 4. The fluid control system according toclaim 2, wherein the outlet of the nozzle has a cross-sectional areawhich is smaller than the cross-sectional area of the control line inthe vicinity of the outlet.
 5. A vehicle brake system for a vehiclewhich includes a tractor and a trailer which can be connected to anddisconnected from the tractor, said brake system including:a relay valvefor supplying fluid to brakes of the vehicle to activate the vehiclebrakes; a fluid supply coupled to the relay valve so that, uponactuation of the relay valve, supply fluid is supplied from the fluidsupply via the relay valve to the vehicle brakes to actuate the vehiclebrakes; a control line having a first control line portion which iscoupled to the tractor and a second control line portion which iscoupled to the trailer, and which is decoupled from the tractor when thetrailer is disconnected from the tractor, the first control line portionhaving a first connector and the second control line portion having asecond connector for detachable connection to said first connector sothat the first and second control line portions can be coupled togetherwhen the trailer is connected to the tractor, the control line beingcoupled to the relay valve so that upon depression of a brake pedal inthe vehicle, a control signal is supplied down the control line to therelay valve to actuate the relay valve; and fluid supply means forsupplying fluid from the fluid supply to the control line to prime thecontrol line when the brake pedal is depressed, the fluid supply meansbeing connected to a front portion of the trailer.
 6. The fluid controlsystem according to claim 5, wherein:the fluid supply means includes anozzle having an outlet directed in the longitudinal direction of thecontrol line for supply of the fluid from the fluid supply in thelongitudinal direction of the control line.
 7. The fluid control systemaccording to claim 6, wherein the fluid supply further includes asolenoid valve for selectively enabling the fluid to flow from the fluidsupply to the control line.
 8. The fluid control system according toclaim 6, wherein the outlet of the nozzle has a cross-sectional areawhich is smaller than the cross-sectional area of the control line inthe vicinity of the outlet.
 9. A fluid control system for a brakesystem, including:a pressurized fluid supply means for supplyingpressurized fluid; a relay valve coupled to the pressurized fluid supplymeans; a control line coupled to the relay valve for supplying a controlsignal to actuate the relay valve to enable the relay valve to supplypressurized fluid from the pressurized fluid supply means to actuatebrakes of a vehicle; and priming fluid supply means coupled to thecontrol line for directing priming fluid in the longitudinal directionof the control line for priming the control line.
 10. The fluid controlsystem according to claim 9, wherein:the priming fluid supply meansincludes a nozzle having an outlet directed in the longitudinaldirection of the control line for supplying the fluid from the fluidsupply in the longitudinal direction of the control line.
 11. The fluidcontrol system according to claim 10, wherein the priming fluid supplyfurther includes a solenoid valve for selectively enabling the fluid toflow from the fluid supply to the control line.
 12. The fluid controlsystem according to claim 10, wherein the outlet of the nozzle has across-sectional area which is smaller than the cross-sectional area ofthe control line in the vicinity of the outlet.